SPC Inquiry for Quad-Aligned Zero -- deprecated since SPC-4 maybe

Ralph Weber roweber at ieee.org
Thu Jan 3 09:32:08 PST 2008

* From the T10 Reflector (t10 at t10.org), posted by:
* Ralph Weber <roweber at ieee.org>
What is wrong with TEST UNIT READY as a way to validate Command Out
and Status In processing?
Curious in Dallas,
Mark Evans wrote:
> * From the T10 Reflector (t10 at t10.org), posted by:
> * "Mark Evans" <Mark.Evans at wdc.com>
> *
> Hi Ralph,
> Now what I think Pat is trying to do is to highlight that setting
> LENGTH to zero in an INQUIRY command is allowed, and that this setting may
> be used as, "...a way of asking to test Command Out and Status In without
> asking to test Data...".  However, I think this is covered.  Why the value
> in the ALLOCATION LENGTH should be set to five or four is already explained
> by the cross references in 6.4.1 INQUIRY command introduction, albeit not
> clearly as my suggested wording, but definitely more succinctly.  Wow.
> Three "ly" adverbs in one sentence -- ha!
> The qualification for the five or four in the ALLOCATION LENGTH field in an
> INQUIRY command as defined in 6.4.1 is only a "should".  Based on that
> zero is allowed as a value in the field for whatever reason.	In addition,
> the second paragraph in Allocation length reads, "An allocation
> length of zero specifies that no data shall be transferred.  This condition
> shall not be considered as an error."  So, 6.4.1 implicitly permits zero as
> an allowed value for an INQUIRY command, and explicity allows a
> value of zero in an ALLOCATION LENGTH field for any command.
> I think that there are many words that could be added to further explain
> setting of the ALLOCATION LENGTH field in an INQUIRY command.  However,
> standard [already] says so."
> Pat, if you want some more words in SPC-4, I'd suggest submitting a
> to T10, but based on what is already in the standard, I think you may have
> tough sledding.
> Regards,
> Mark Evans
> Western Digital Corporation
> 5863 Rue Ferrari
> San Jose,  CA  95138
> Email: mark.evans at wdc.com
> Office: 408.363.5257
> Fax: 408.363.5139
> Cell: 408.391.780
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